This invention concerns copying apparatus in which an image is formed using thermally developable photosensitive materials.
Conventionally, electrophotographic systems, ink jet systems, etc. have been used for copying color originals. In electronic copying systems, electronic latent images corresponding to an original are generally formed on a charged photosensitive drum by exposing the color original using blue, green and red color separation filters. The colored image is reproduced by developing each of the latent images using a succession of yellow, magenta, cyan, etc. color toners, transferring the colored images formed with each of the color toners, in alignment, onto the same sheet of recording paper, fixing the image with heat, etc. With the ink jet system, the color original is color separated using color filters, etc. and quantities corresponding to the intensities of the colors are stored in a memory. Subsequently, ink of each color is discharged from nozzles in accordance with the memory content to reproduce the colored image.
Apparatus in which the desired color original is copied using silver halide color photosensitive material is also known. For example, the color copying apparatus available commercially under the trade name "Cibachrome Color Copy CC-001" (made by the Ciba-Geigy co.) is a copying apparatus in which a colored image is reproduced using a silver dye bleach type (SDB type) color photosensitive material in which azo dyes are combined with photosensitive silver halide. In such copying apparatus where color photosensitive materials are used there is no need for a memory for storing the image information like that used with the ink jet systems and the problem of color fringing, which arises because of the alignment of a plurality of toner images as used in electronic copying systems, does not arise, and there is a further advantage in that high quality color images can be reproduced with a single exposure.
In normal copying apparatus the original document takes the form of a color positive and a reversal color photosensitive material in the form of a multi-layer color photosensitive material with which a color positive image can be obtained from a color positive original. Multi-layer photosensitive materials consisting of photosensitive silver halide emulsion layers generally form colored images by means of an alkaline development process following exposure. However, in the case of a reversal color photosensitive material, the color positive image is obtained via a complicated process including a stage in which the exposed parts of the silver halide emulsion layers after exposure are subjected to a black and white development process, a stage in which the unexposed parts of the silver halide emulsion layers are exposed to light, a stage in which the unexposed parts of the silver halide emulsion layers which have been exposed at this time are subjected to a color development process, and a stage in which the material is subjected to a bleach-fixing process in order to remove the silver image which has been formed by the development processes. Furthermore, complicated processing involving at least 3 stages is normally required to obtain a colored image from the aforementioned SDB type color photosensitive materials.
As has been described above, color separation of the colored original must be carried out to reproduce a colored image using the electronic copying system or the ink jet system and so at least three exposures are required and a very large memory may be required to store the image information. Moreover, in the electronic copying system, the image quality is reduced by color fringing, etc., and with the ink jet system, there is a further disadvantage in that a long period of time is required to form the copy image. Furthermore, in copying apparatus in which color photosensitive materials are used, the post exposure development processing is complex and additional skill is required to managing the processing baths and the apparatus is large in size and the manufacturing cost is high.
It is also known to obtain colored images by thermal development. Thermally developable color photosensitive materials with which an image can be obtained by thermal development and the processing thereof have been described on pages 242-255 of "The Fundamentals of Photographic Engineering, Non-silver Halide"Vol. (1982, published by Corona), on page 40 of "Image Information", published in April 1978, and on pages 32-33 of Neblett's Handbook of Photography and Reprography, 7th Ed., (published by the Van Nostrand Reinhold Company).
Additionally, other methods have been suggested for obtaining color images by thermal development. Thus, methods in which a mobile dye is released imagewise by heating and the mobile dye transferred by means of a solvent such as water to a dye fixing material (image receiving material) which has a mordant, methods in which the dye is transferred to a dye fixing material by means of a high boiling point organic solvent, methods in which the dye is transferred to the dye fixing material by means of a hydrophilic hot solvent which is incorporated into the dye fixing material, and methods in which the mobile dye is thermally diffusible or sublimable and transferred to a dye receiving material have been suggested. See U.S. Pat. Nos. 4,463,079; 4,474,867; 4,478,927; 4,507,380; 4,500,626; and 4,483,914; and Japanese Patent application (OPI) Nos. 149,046/83; 149,047/83; 152,440/84; 154,445/84; 165,054/84; 170,548/84; 168,469/84; 174,832/84; 174,833/84; 174,834/84; and 174,835/84. With progress being made in office automation, the space occupied by machinery is constantly increasing and miniaturization of machinery is becoming an essential requisite.